I have a bone to pick with the end of this song: it really annoys me when a song that’s been in a minor key switches to major right at the end. You never hear a major song turning minor right at the end (watch the comments fill up with examples). It’s the worst sort of discrimination in the world by far.
It’s worth keeping your index finger barred on the third fret to make for easier chord changes. But that does make it tough on the left hand because you’re barring for the whole song. So if it starts feeling sore while you’re practicing take a break.
For the longer strums you can use old faithful:
d – d u – u d –
And for the short ones just two down strums:
d – d –
The tricky bit comes at the end of the choruses. On the C7 do old faithful then two down strums. One down strum each for Db7 and C7. Two down strums each for Fm and Db7. Then back to old faithful for C7.
On the Fm at “things that you do to me” she plays crochet triplets. But old faithful will work fine there if you’re not comfortable with those yet.